Polyester polycondensation with catalyst and a catalyst enhancer

ABSTRACT

The present invention is based upon the discovery that nontitanyl oxalates can enhance the catalytic functionality of titanyl oxalate catalysts. This invention provides a novel catalytic composition containing a titanyl oxalate catalyst and a metallic oxalate catalyst enhancer and optionally containing a metallic cocatalyst such as an antimony based catalyst. A synergistic relationship has been discovered between titanyl oxalate catalyst and the catalyst enhancer. A synergistic relationship has also been discovered between the titanyl oxalate catalyst, catalyst enhancer and a metallic cocatalyst such as antimony oxide or antimony triacetate. Also provided is an improved process of producing polyester by the polycondensation of polyester forming reactants in the presence of a catalytically effective amount of a polycondensation catalyst, wherein the improvement comprises utilizing, as the polycondensation catalyst, the novel catalyst composition containing a titanyl oxalate such as lithium titanyl oxalate and a catalyst enhancer such as a nontitanyl metallic oxalate like lithium oxalate and optionally containing a metallic catalyst such as antimony oxide or antimony triacetate. The improved process produces an improved polyester having lower acetaldehyde numbers and good color. The titanyl oxalate/catalyst enhancer composition can be used as a polycondensation catalyst in combination with other catalysts to achieve synergistic catalytic activity. Preferred is a combination of lithium or potassium titanyl oxalate, Li 2  or K 2 TiO(C 2 O 4 ) 2 , lithium or potassium oxalate, Li 2  or K 2 (C 2 O 4 ) 2  with antimony oxide or antimony triacetate or antimony trisglycoxide.

[0001] REFERENCE TO RELATED APPLICATION

[0002] This application is a continuation-in-part of U.S. patentapplication Ser. No. 09/747,115, filed Dec. 22, 2000, which claimspriority of U.S. Provisional Application No. 60/175,006, filed Jan. 7,2000, which disclosures are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0003] This invention relates to synergistic combinations of titaniumcontaining catalysts and catalyst enhancers of carboxylic acid or oxalicacid or their Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba and ammonium saltsthat are useful for manufacturing polyesters. The synergisticcombination of the titanium containing catalysts with a catalystenhancer such as an oxalic acid, an oxalic acid salt or a carboxylicacid or a carboxylic acid salt provides fast reactions with improvedproperties such as reduced acetaldehyde content and good colorproperties for the resulting polyester at substantially reduced catalystlevels.

DESCRIPTION OF THE PRIOR ART

[0004] Polycondensation reactions that produce polyesters require anextremely long period of time that is significantly reduced by asuitable catalyst. Various types of catalysts are used to shorten thereaction time. For example, antimony trioxide antimony triacetate andantimony trisglycoxide are generally used as polycondensation catalysts.

[0005] Titanyl oxalate compounds have been suggested as catalysts forpolycondensation reactions to produce polyesters. However, titanyloxalate catalysts when used as polycondensation catalysts for polyestershave caused color problems in the resulting polyester.

[0006] Polyesters are obtained by esterification, ester interchange orpolycondensation of dibasic acids such as terephthalic acid andisophthalic acid or esters thereof, functional derivatives of acidchlorides and glycols such as ethylene glycol and tetramethylene glycolor oxides thereof and functional derivatives of carbonic acidderivatives. In this case, a single polyester is obtained when onedibasic acid component and glycol component are used. Mixed copolyesterscan be obtained when at least two or more types of dibasic acidcomponent and glycol component are mixed, esterified or subjected toester interchange and then subjected to polycondensation. When a singlepolyester or two or more initial polycondensates of a mixed copolyesterare subjected to polycondensation, an ordered polyester is obtained. Inthis invention, the term polyester is a general designation for thesethree types.

[0007] Prior literature has disclosed titanyl oxalate compounds for useas polycondensation catalysts for polyesters. The titanyl oxalatecompounds disclosed include potassium titanyl oxalate, ammonium titanyloxalate, lithium titanyl oxalate, sodium titanyl oxalate, calciumtitanyl oxalate, strontium titanyl oxalate, barium titanyl oxalate, zinctitanyl oxalate and lead titanyl titanate. However, based upon theexamples in such literature references, only potassium and ammoniumtitanyl oxalate have actually been used to catalyze the polyesterforming reaction. See for example Japanese Patent Publication 42-13030,published on Jul. 25, 1967. European Patent application EP 0699700 A2published Mar. 6, 1996 assigned to Hoechst and entitled “Process forproduction of Thermostable, Color-neutral, Antimony-Free Polyester andProducts Manufactured From It” discloses the use as polycondensationcatalyst, however only potassium titanyl oxalate and titaniumisopropylate were used for such a catalyst, and, while improved colorand antimony free polyester are disclosed, cobalt or optical brightenerswere also employed. Other patents have disclosed potassium titanyloxalate as a polycondensation catalyst for making polyester such as U.S.Pat. No. 4,245,086, inventor Keiichi Uno et al., Japanese Patent JP06128464, Inventor Ishida, M. et al. U.S. Pat. No. 3,951,886, entitled“Process of Producing Polyester Resin” of Hideo, M. et al, at column 3,line 59 to column 4, line 10, contains a disclosure of titanyl oxalatecatalysts for polyesters including a listing of many types of titanyloxalate catalyst. However, only potassium titanyl oxalate and ammoniumtitanyl oxalate were used in the examples and lithium titanyl oxalatewas not even listed among their preferred titanyl oxalate catalysts.

[0008] Titanium based catalysts have shown very high polycondensationactivity, however; the resulted polyesters are yellowish color whichwill limit their applications. Therefore, prior art activity has beendirected towards the development of modified titanium catalysts.Titanium compounds are not a good sole catalyst. Ti requires acocatalysts or modifiers/promoters to form composite catalyst. Titaniumcompounds in the general formula of Ti(OR)₄, Ti^((III))Ti^((IV))_(y)O_((3+4y)/2), RO[Ti(OR)₂O]_(n)R have been widely claimed by others.Cocatalysts or modifiers/promoters, such as antimony compounds, tincompounds, zirconium compounds, silicon compounds, cobalt compound,aluminum compounds, alkali metal compounds, rare earth metal compounds,magnesium compounds, germanium compounds, zinc compounds, lanthanideseries compounds, phosphorus compounds, halides, sulfur containingcompounds, ammonia hydroxide, and amines, have been claimed togetherwith Ti compounds.

[0009] U.S. Pat. No. 6,166, 170, E.I. du Pont de Nemours and Company,issued on Dec. 26, 2000 discloses a catalyst composition of a titaniumcompound, a complexing agent, and an aqueous solution of hypophosphorousacid or a salt. The titanium compound has a general formula, Ti(OR)₄,combined with a zirconium compound, Zr(OR)₄. The complex agents arehydroxycarboxylic acids, alkanolamines, aminocarboxylic acids and theircombinations of two or more.

[0010] U.S. Pat. No. 6,066,714, E.I. du Pont de Nemours and Company,issued on May 23, 2000, discloses an organic titanium compound, aphosphorus compound, an amine, and a solvent as a catalyst. The organiccompound is Ti(OR)₄. The phosphorus compound is either(RO)_(x)(PO)(OH)_(3−x) or (RO)_(y)(P₂O₃)(OH)_(4−y). The amine is atertiary amine. Aluminum, cobalt, antimony compounds and theircombination were claimed as cocatalysts.

[0011] U.S. Pat. No. 6,034,203, E.I. du Pont de Nemours and Company,issued on Mar. 7, 2000, discloses a catalytic process that can be usedin oligomerization, polymerization, or depolymerization. The catalysthas the formula of M_(x)Ti^((III))Ti^((IV)) _(y)O_((x+3+4y)/2), where Mis an alkali metal, such as Li; x and y are numbers greater than orequal to zero wherein if x equals zero, y is a number less than ½.

[0012] U.S. Pat. No. 5,981,690, E.I. du Pont de Nemours and Company,issued on Nov. 9, 1999. This patent shows a catalyst solution containingan organic titanate ligand, organic silicates and/or zirconates, andphosphorus compounds. Titanium has a formula of Ti(OR)₄; silicon andzirconium compounds can be organic ortho silicate and zirconate;phosphorus compound can be an organic phosphonic or phosphinic acid. Thesolvent used was ethylene glycol. The catalyst was claimed to be used infabrication of PET, PEI, PPT, PBT, and etc.

[0013] U.S. Pat. No. 5,866, 710, Tioxide Specialties Limited, issued onFeb. 2, 1999 (EP 0 812 818 Al, published on Dec. 17, 1999). A process ofpreparing an ester is disclosed in the presence of a catalyst and abase, the product from orthoesters and condensed orthoesters ofzirconium and titanium. The orthoesters have the formula of M(OR)₄; thecondensed orthoesters, RO[M(OR)₂O]R; where M is either zirconium ortitanium. This compound can be illustrated as the following,

M(OR)₄, if n=1

(RO)₃MOM(OR)₃, if n=2

(RO)₃MOM(OR)₂OM(OR)₃, if n=3,

[0014] and etc.

[0015] The base can be selected sodium hydroxide, potassium hydroxide,ammonium hydroxide, sodium carbonate, magnesium hydroxide and ammonia.

[0016] WO 00/71252 Al, ACMA Limited, published on Nov. 30, 2000. Anesterification catalyst composition was disclosed. The catalystcontains 1) hydrolysis product of orthoesters and condensed orthoestersof titanium, zirconium or aluminum; 2) an alcohol containing at leasttwo hydroxyl groups; 3) an organophosphorus compound containing at leastone P—OH group and a base; 4) a compound of germanium, antimony or tin.

[0017] WO 99/28033 Al, Tioxide Specialties, published on Jun. 10, 1999.An esterification catalyst composition was disclosed. The catalystcontains 1) hydrolysis product of orthoesters and condensed orthoestersof titanium, zirconium or aluminum; 2) an alcohol containing at leasttwo hydroxyl groups; 3) an organophosphorus compound containing at leastone P-OH group and a base.

[0018] WO 97/47675 Al, Imperial Chemical Industries PLC, published onDec. 18, 1997 also EP 0906356 jointly with E. I. Du Pont De Nemours &Company Inc. A catalyst is disclosed that is obtained by reacting analkyl titanate or alkyl zirconate, an alcohol, a 2-hydroxy carboxylicacid and a base. A cobalt (II) salt, a phosphorus compound, and a sodiumcompound were claimed as catalyst components.

[0019] U.S. Pat. No. 5,874,517, Hoechst Celanese Corporation, issued onFeb. 23, 1999. An improved low acetaldehyde process was disclosed. Theprocess utilized mixed Ti and Sb catalysts, however; potassium titanyloxalate was suggested as a sole catalyst (col. 6, lines 21 and 22).Potassium titanyl oxalate as a polycondensation catalyst was claimed inclaims 15 to 20.

[0020] U.S. Pat. No. 5,902,873, General Electric Company, issued on May11, 1999; (EP 0 909 774 Al, published on Apr. 21, 1999. A catalystcomposition for the preparation of a polyester on copolyester isdisclosed. The catalyst was composed of 1) a titanium or zirconium basedcompound, general formula, Ti(OR)₄ or Zr(OR)₄, the titanium compoundswere water-stable; 2) a lanthanide series compound, such as lanthanum,samarium, europium, erbium, terbium, and cerium; 3) a hafnium basedcompound; 4) a phosphate-forming compound, such as alkali metalphosphates, alkali metal phosphates, alkali hypophosphates, and alkalimetal polyphosphates. The combination of the above components wasclaimed. In particular, titanium oxide acetylacetonate was claimed (inclaim 3, col. 13, lines 52 and 53).

[0021] U.S. Pat. No. 6,133,404, National Institute of Technology andQuality, issued on Oct. 17, 2000. A polyester and formation process isdisclosed in the presence of a composite catalyst that consists of atitanium compound, a zinc compound, an antimony compound, and aphosphorous compound. This catalyst improved the rate of polyesterproduction and properties of the polymers, in particular,biodegradability of the polymer. The titanium compound has the followinggeneral formula,

Ti(OR)₄,

(RO)₄TiHP(O)(OR′)₂

ROTi[OM(O)R″]₃,

[0022] where M is selected from carbon atom, phosphorous atom, sulfuratom, and their mixtures.

[0023] The zinc compound can be zinc oxide, zinc acetate, zinc chloride,zinc hydroxide and their mixtures. An antimony compound can be selectedfrom antimony chloride, antimony acetate, antimony oxide and theirmixtures. A phosphorous compound can be one of the following, Phosphoricacid compounds, phosphite compounds, phosphonic acid compounds,phosphinic acid compound, and their mixtures.

[0024] U.S. Pat. No. 5,714,570, Korea Institute of Science andTechnology, issued on Feb. 3, 1998. A method for the preparation ofpolyester by use of a composite catalyst was revealed. The compositecatalyst consists of a compound of Sb, a compound of Ti, and a compoundof Sn. A compound of Ti has a general formula of (R₁O)₄TiHP(O)(OR₂)₂,and Tin compound, (R₃)₂SnX, where X is selected from sulfur, oxygen,halogen, and a compound containing an ether, a thio or an ester bond. Inparticular, potassium titanium oxyoxalate was claimed as shown in claim9 (col. 10, lines 52 and 53) other metals (such as germanium, zinc,manganese, alkali, and alkali earth) compounds were also claimed. It wasdisclosed that antioxidant, such as a hindered phenol, was used in theprocess.

[0025] U.S. Pat. No. 6,143,837, Sinco Ricerche, S.P.A, issued on Nov. 7,2000. A process of preparation of polyester resin utilizing Ti compoundcatalyst was disclosed. The activity of Ti catalysts was shown to befour time higher than S21 catalyst. The titanium compounds can beselected from the group consisting of alkoxides of titanium, acetylacetonates of titanium, dioxide of titanium, and titanium phosphites.Silica mixed with Ti was used in their examples (but not claimed). Acobalt compound was suggested to be used as a colorants.

SUMMARY OF THE INVENTION

[0026] The present invention is based upon the discovery of asynergistic combination of a titanium containing catalyst and a catalystenhancer. This invention provides a novel catalytic mixture comprising atitanium containing catalyst of the formula X_(m)TiO(C₂O₄)₂(H₂O)_(n),where X is selected from the group consisting of H, Li, Na, K, Rb, Cs,Be, Mg, Ca, Sr, Ba, and ammonium, m=1 or 2; and a catalyst enhancercomprising oxalic acid or carboxylic acid containing 1 to 26 carbonatoms or their corresponding Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, orammonium salt. Also provided is a novel enhanced catalyst mixturecomprising a titanium compound of the formula X_(m)TiY_(o) with Xselected from the group consisting of: H, Li, Na, K, Rb, Cs, Be, Mg, Ca,Sr, Ba and ammonium, m=1 or 2, Y is a ligand of the formulaC_(a)H_(b)O_(c), a=0 to 30, b=0 to 60, and c=1 to 10; o=2, 3, 4, and acatalyst enhancer of an oxalic acid or its corresponding Li, Na, K, Rb,Cs, Be, Mg, Ca, Sr, Ba or ammonium salt. An improved three componentenhanced catalyst mixture can be obtained by the addition of secondcatalyst to either of the above enhanced catalyst mixtures, the secondcatalyst being a compound containing antimony or germanium. Alsoprovided are enhanced antimony containing catalysts comprising themixture of an antimony containing catalyst and an enhancer of an oxalicacid or its corresponding Li, Na, K, Rb Cs, Be, Mg, Ca, Sr, Ba orammonium salt.

[0027] This invention also provides an improved process of producingpolyester by the polycondensation of polyester forming reactants in thepresence of a catalytically effective amount of a polycondensationcatalyst, wherein the improvement comprises utilizing, as thepolycondensation catalyst, the synergistic combination of a titaniumcontaining catalyst and the catalyst enhancer described in the precedingparagraph. A novel polyester is also provided containing the synergisticcombination of a titanium containing catalyst and the catalyst enhancerdescribed in the preceding paragraph. The improved process produces animproved polyester having lower acetaldehyde numbers and good color. Thetitanium containing catalyst and catalyst enhancer composition can beused as a polycondensation catalyst in combination with other catalyststo achieve synergistic catalytic activity.

DETAILED DESCRIPTION OF THE INVENTION

[0028] The production of polyester by polycondensation of polyesterforming reactants is well known to those skilled in the polyester art. Aconventional catalyst for the reaction is antimony oxide. The presentinvention is based upon the discovery of a synergistic relationshipbetween titanium containing catalysts and carboxylic or oxalate catalystenhancers. The catalyst and catalyst enhancer is surprisingly superiorin catalyst performance for polycondensation reactions by providing goodcatalyst activity at reduced catalyst loadings and superior brightnessin the resulting polyester.

[0029] Reactants for forming polyesters via a polycondensation reactionare well known to those skilled in the art and disclosed in patents suchas U.S. Pat. No. 5,198,530, inventor Kyber, M., et al., U.S. Pat. No.4,238,593, inventor B. Duh, U.S. Pat. No. 4,356,299, inventor Cholod etal, and U.S. Pat. No. 3,907,754, inventor Tershasy et al, whichdisclosures are incorporated herein by reference. The art is alsodescribed in “Comprehensive Polymer Science, Ed. G. C. Eastmond, et al,Pergamon Press, Oxford 1989, vol. 5, pp. 275-315, and by R. E. Wilfong,J. Polym. Science, 54(1961), pp. 385-410. A particularly importantcommercial specie of polyester so produced is polyethylene terephthalate(PET).

[0030] In addition to catalyzing polycondensation reactions, thesynergistic catalyst combinations of the present invention are effectivefor catalyzing esterification and transesterification reactions whenused in catalytically effective amounts with reactants known toparticipate in esterification or transesterification reactions. Acatalytically effective amount is suitable.

[0031] An improved three component enhanced catalyst composition can beobtained by the addition of second catalyst to enhanced catalystcomposition defined above, the second catalyst being a compoundcontaining antimony or germanium.

[0032] TITANIUM OXALATE CATALYSTS:

[0033] Examples of titanium oxalate catalysts of the formulaX_(m)TiO(C₂O₄)₂(H₂O)_(n), where each X is independently selected fromthe group consisting of H, Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba andammonium, m=1 or 2 are well known. Titanyl oxalates comprise compoundsof the formula: X_(m)TiO(C₂O₄)₂(H₂O)_(n), where X is selected from thegroup consisting of: H, Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba, m=1 or2. Titanyl oxalates include metallic titanyl oxalates of the formulaM₂TiO(C₂O₄)₂(H₂O)_(n) wherein each M is independently selected frompotassium, lithium, sodium and cesium such as lithium or potassiumtitanyl oxalate and nonmetallic titanyl oxalates such as ammoniumtitanyl oxalate. The titanyl oxalate may be anhydrous (n=0) or containsome water of hydration, i.e. n representing the amount of water ofhydration. Preferred are H, Li, Na, K, Ca, Cs and ammonium.

[0034] CARBOXYLIC ACID OR SALT:

[0035] Examples of a catalyst enhancer for the titanium oxalatecatalysts are a carboxylic acid containing 1 to 26 carbon atoms or itscorresponding carboxylic acid salt having an anion selected from thegroup consisting of Li, Na, K, Rb Cs, Be, Mg, Ca, Sr, Ba and ammonium.As used herein, “carboxylic acid” includes dicarboxylic acid. Examplesof such carboxylic acids or salts are well known and include sodiumacetate, sodium propionate, sodium citrate, sodium butyrate, sodiumformate, sodium fumarate, malonic acid, potassium acetate, potassiumbenzoate, succinic acid, glutaric acid, adipic acid, maleic acid.Preferred are potassium acetate, potassium benzoate.

[0036] Titanium Containing Catalysts:

[0037] Examples of titanium containing compounds of the formulaX_(m)TiY_(o) with X selected from the group consisting of: H, Li, Na, K,Rb, Cs, Be, Mg, Ca, Sr, Ba and ammonium, m=0, 1, or 2, Y is a ligand ofthe formula C_(a)H_(b)O_(c), a=0 to 30, b=O to 60, and c=1 to 10; o=2,3, 4, include: acetylacetonate (a=5, b=7, and c=2); i-propoxide (a=3,b=7, and c=l); butoxide (a=4, b=9, and c=1);bis(2,2,6,6,-tetramethy-3,5-heptanedionato), i.e. a=11, b=19, and c=2.Preferred are acetylacetonate, i-propoxide,bis(2,2,6,6,-tetramethy-3,5-heptanedionato).

[0038] Oxalic Acid or Salt:

[0039] Examples of a catalyst enhancer for said titanium containingcompounds are oxalic acids or its corresponding Li, Na, K, Rb Cs, Be,Mg, Ca, Sr, Ba, or ammonium oxalic acid. Preferred are H, Li, Na, K, Ca,Cs, and ammonium.

[0040] Antimony Containing Catalysts:

[0041] Examples of antimony containing catalysts that can be added tothe synergistic combination of enhanced titanium oxalate or titaniumcontaining catalysts defined above are Sb₂O₃, Sb(CH₃COO)₃, andSb₂(OCH₂CH₂O)₃.

[0042] Germanium Containing Catalysts:

[0043] Examples of germanium containing catalysts that can be added tothe synergistic combination of enhanced titanium oxalate or titaniumcontaining catalysts defined above are GeO₂, Ge(OC₂H₅)₄, Ge[OCH(CH₃)₂]₄,Ge(OCH₃)₄. Preferred is GeO₂.

[0044] Enhanceable Antimony Containing Catalysts:

[0045] Examples of antimony containing catalysts that can be enhancedwith a carboxylic acid or salt or an oxalic acid or salt are Sb₂O₃,Sb(CH₃COO)₃, Sb₂(OCH₂CH₂O)₃.

[0046] Cocatalyst:

[0047] Cocatalysts that function in combination with the titaniumcontaining catalyst and the enhancer include antimony triacetate,Sb(CH₃COO)₃, antimony glycoxide, Sb₂(OCH₂CH₂O)₃, antimony oxide.(Sb₂O₃).

[0048] An effective amount for enhancing the catalytic activity oftitanyl oxalate catalysts or a titanium containing catalyst is at leastabout 0.1 part of enhancer per part of titanyl oxalate catalyst.Preferred is from about 0.1 part to about 100 parts enhancer per part ofcatalyst based upon the total weight of titanium in the catalyst.

[0049] When used in combination with an enhancer, a catalyticallyeffective amount of titanium containing catalyst should be added to thepolyester forming reactants, generally at least 0.1 part based upon theweight of titanium. Preferred is from about 1 part to about 40 parts permillion of catalyst based on the weight titanium in the catalyst and theweight of the of polyester forming reactants.

[0050] When used in combination with an enhancer, a catalyticallyeffective amount of an antimony containing catalyst should be added tothe polyester forming reactants. Preferred is from about 1 part to about240 parts per million of catalyst based on the weight antimony in thecatalyst and the weight of the of polyester forming reactants. Forenhancing an antimony containing catalyst, an effective amount for of anenhancer for the catalytic activity of an antimony containing catalystis at least about 0.1 part of enhancer per part of antimony containingcatalyst based the weight of antimony in said antimony containingcatalyst. Preferred is from about 0.1 part to about 80 parts enhancerper part of catalyst based upon the total weight of titanium in thecatalyst.

[0051] The preferred amount of a antimony or germanium containingcatalyst for use in combination with the enhanced titanium oxalate ortitanium containing catalyst described above is from about 0.1 parts toabout 80 parts based upon the weight of titanium. Preferred is from 1 to40 parts of antimony or germanium containing catalyst.

[0052] The catalyst and enhancer mixtures of the present invention areused to make polyester typically by first dissolving them in a solventthat is compatible with polyester forming reactants, or preferable inone of the reactants itself, such as ethylene glycol.

[0053] The synergistic performance of the catalyst enhancer incombination with one or more catalysts for a polycondensation reactionfor the production of PET resin is shown by the following examples.

EXAMPLES

[0054] In a polyester polycondensation reaction, acetaldehyde (AA) is anundesirable polymerization by-product. Polymerization rate is measuredas rate at which intrinsic viscosity (IV) increases during reaction.Intrinsic viscosity change is an indication of the degree ofpolymerization that has occurred during the reaction.

Examples 1-20 and A-G

[0055] Catalyst evaluation was performed with a {fraction (3/16)}stainless steel, 2 L reactor, fitted with a ball valve at the bottom ofthe reactor. The vessel was equipped with 3 inlet ports, one outletport, one thermowell port and one pressure transducer port, and wasvertically stirred by an electric motor with amperage monitoring. Thelaboratory experimental were all conducted on a 4.0 mole scale, using aspolyester forming reactants, BHET and a normal bottle resin autoclaverecipe. The experimental catalysts were added at the time of BHETcharging.

[0056] Bis(2-hydroxyethyl)terephthalate (BHET) and catalyst were addedto the reactor and the contents blanketed with nitrogen. The mixtureswere heated under reduced pressure with constant stirring. The ethyleneglycol (EG) produced during the polymerization was removed and trapped.The polymerization was at 280° C. , under the vacuum of typically around1 torr. The reaction was terminated when the stirrer torque reached alevel, indicated by amperage to the stirrer motor, typical for a polymerof IV ˜0.6. The molten state polymer under nitrogen (containing lessthan 2 ppm of oxygen) blanket was discharged from the bottom ball valveand quenched into a bucket filled with cold water. ¼″ diameter and{fraction (1/16)}″ thick pellets (for color measurement) were made byfilling the molten polymer in a press molder and chilled immediately incold water.

[0057] The solution intrinsic viscosity (IV) was measured by followingthe ASTM D 4603 method. Acetaldehyde (AA) was measured at 150° C. usinggas chromatography (GC) equipped with a headspace analyzer. Thebrightness (L*) and yellowness (b*) were determined by the Hunter Lab'sinstrument and method.

[0058] Twenty-seven examples were performed using the above procedureand various catalysts and catalyst enhancer amounts.

[0059] Example A catalyst−180 ppm potassium oxalate−reaction time=124mins.

[0060] Example B catalyst−2 ppm titanium from potassium titanyloxalate−reaction time=118 mins.

[0061] Example C catalyst−6 ppm titanium potassium titanyloxalate−reaction time=71 mins.

[0062] Example D catalyst−25 ppm antimony from antimony (III)oxide−reaction time=122 mins.

[0063] Example 1 catalyst−2 ppm titanium from potassium titanyloxalate+90 ppm potassium oxalate−reaction time=111 mins.

[0064] Example 2 catalyst−90 ppm potassium oxalate+25 ppm antimony fromantimony (III) oxide−reaction time=120 mins.

[0065] Example 3 catalyst−180 ppm potassium oxalate+50 ppm antimony fromantimony (III) oxide−reaction time=130 mins.

[0066] Example 4 catalyst−90 ppm potassium oxalate+100 ppm antimony fromantimony (III) oxide−reaction time=112 mins.

[0067] Example 5 catalyst−2 ppm titanium from potassium titanyloxalate+90 ppm potassium oxalate+25 ppm antimony from antimony (III)oxide−reaction time=105 mins.

[0068] Example E catalyst−240 ppm antimony from antimony (III)oxide−reaction time=90 mins.

[0069] Example F catalyst−240 ppm antimony from antimony (III)oxide−reaction time=100 mins.

[0070] Example 6 catalyst−2 ppm titanium from potassium titanyloxalate+90 ppm potassium oxalate+25 ppm antimony from antimony (III)oxide−reaction time=73 mins.

[0071] Example 7 catalyst−2 ppm titanium from potassium titanyloxalate+90 ppm ammonium oxalate+25 ppm antimony from antimony (III)oxide−reaction time=78 mins.

[0072] Example 8 catalyst−2 ppm titanium from ammonium titanyloxalate+90 ppm potassium oxalate+25 ppm antimony from antimony (III)oxide−reaction time =79 mins.

[0073] Example 9 catalyst−2 ppm titanium from ammonium titanyloxalate+90 ppm ammonium oxalate+25 ppm antimony from antimony (III)oxide−reaction time=77 mins.

[0074] Example 10 catalyst−2 ppm titanium from potassium titanyloxalate+90 ppm potassium acetate+25 ppm antimony from antimony (III)oxide−reaction time=81 mins.

[0075] Example 11 catalyst−2 ppm titanium from potassium titanyloxalate+90 ppm potassium benzoate+25 ppm antimony from antimony (III)oxide−reaction time=72 mins.

[0076] Example 12 catalyst−2 ppm titanium frombis(2,2,6,6-tetramethy-3,5-heptanedionato) oxotitanium+90 ppm potassiumoxalate+25 ppm antimony from antimony (III) oxide−reaction time=72 mins.

[0077] Example 13 catalyst−2 ppm titanium fromdi(i-propoxide)bis(2,2,6,6-tetramethyl-3,5-heptanedionato)titanium+90ppm potassium oxalate+25 ppm antimony from antimony (III) oxide−reactiontime=100 mins.

[0078] Example 14 catalyst−2 ppm titanium from titanium oxideacetylacetonate+90 ppm potassium oxalate+25 ppm antimony from antimony(III) oxide−reaction time=114 mins.

[0079] Example 15 catalyst−2 ppm titanium from potassium titanyloxalate+90 ppm calcium oxalate+25 ppm antimony from antimony (III)oxide−reaction time=109 mins.

[0080] Example 16 catalyst−2 ppm titanium from potassium titanyloxalate+45 ppm oxalic acid+25 ppm antimony from antimony (III)oxide−reaction time=108 mins.

[0081] Example 17 catalyst−2 ppm titanium from potassium titanyloxalate+90 ppm sodium oxalate+25 ppm antimony from antimony (III)oxide−reaction time=108 mins.

[0082] Example 18 catalyst−2 ppm titanium from lithium titanyloxalate+50 ppm lithium oxalate+25 ppm antimony from antimony (III)oxide−reaction time=102 mins.

[0083] Example G catalyst−60 ppm germanium from germanium oxide−reactiontime=149.

[0084] Example 19 catalyst−10 ppm germanium from germanium oxide+90 ppmpotassium oxalate−reaction time=130 mins.

[0085] Example 20 catalyst−2 ppm titanium from potassium titanyloxalate+90 ppm potassium oxalate+7 ppm germanium from germaniumoxide−reaction time=123 minutes.

EXAMPLE RESULTS AND DISCUSSION

[0086] AMOUNT POLY TIME AA EXAMPLE (mg) (mins.) IV (ppm) L* b*  A 185.5124 0.252 66.1 80.3 3.6  B 15.4 118 0.583 52.9 76.6 8.3  C 46.5 71 0.58342.7 78.4 7.1  D 30.8 122 0.230 53.7 na na  1 106.4 111 0.591 52.6 76.67.7  2 125.9 120 0.461 24.4 68.3 5.8  3 246.8 130 0.536 46.1 80.4 6.5  4215.6 112 0.587 38.3 77.6 6.0  5 137.0 105 0.596 42.4 81.4 5.3  B 298.990 0.593 34.9 69.9 5.3  F 296.7 100 0.586 34.3 70.0 5.9  6 137.2 730.514 26.8 79.6 3.4  7 137.6 78 0.520 32.4 77.3 4.7  8 133.6 79 0.51933.8 80.4 4.1  9 134.2 77 0.542 19.4 78.6 5.6 10 137.1 81 0.538 22.078.3 5.3 11 208.9 72 0.534 18.2 75.5 6.1 12 140.7 72 0.540 19.9 66.4 5.213 145.5 100 0.590 45.6 65.7 5.2 14 134.3 114 0.589 42.9 71.9 6.8 15137.9 109 0.597 42.9 78.3 6.2 16 92.7 108 0.607 39.7 76.2 6.9 17 137.5108 0.600 43.0 80.8 5.0 18 95.7 102 0.583 37.7 80.4 5.9  G 89.8 1490.586 43.9 79.9 5.1 19 106.3 130 0.494 41.3 64.9 3.7 20 117.9 123 0.58342.5 74.1 8.4

[0087] In comparing examples A, B, C and 1, 180 ppm potassium oxalatealone a polymer with a IV of 0.252 after 124 minutes. Using example B asa baseline, mer with a similar IV, 118 minutes were needed for 2 ppmtitanium in potassium titanyl oxalate while only 71 minutes were neededfor 6 ppm titanium as shown in example C. The addition of potassiumoxalate to potassium titanyl oxalate enhanced the rate of polymerizationas can be seen in example 1.

[0088] In comparing examples A, D, 2, 3, 4 E and F, 180 ppm potassiumoxalate alone produced a polymer with an IV of 0.252 after 124 minutes,25 ppm of antimony in antimony oxide produced a polymer with an IV of0.230 after 122 minutes. It is shown in examples 2, 3, and 4 that theaddition of potassium oxalate to antimony enhanced the polymerizationrate, reduced the amount of acetaldehyde, and also increased thebrightness as compared to examples E and F.

[0089] In comparing examples B and 5, using the combination of potassiumtitanyl oxalate, potassium oxalate, and antimony oxide, thepolymerization rate was faster, the acetaldehyde concentration waslower, the resulting polymer was more brighter and less yellow.

[0090] In comparing examples 5, E and F, the three component catalystproduced more brighter and less yellow polymer than antimony oxide. Itis conceivable that the rate for three components can be furtherenhanced and the amount of acetaldehyde in the resulting polymer can befurther reduced by adjusting the composition of the three components.

[0091] In comparing examples 6 to 9, replacing potassium with ammoniumin three components catalyst reduced the polymerization rate slightly.The resulting polymer by ammonium containing catalyst was slightly moreyellow.

[0092] In comparing examples 5, 6, 10 to 14, different ligands such asoxalate, acetate, benzoate, bis 2,2,6,6,-tetramethy-3,5-heptanedionate,i-propoxidate, acetylacetonate have been used. The catalysts containingthese ligands polymerized BHET in a comparable rate with oxalatecontaining catalyst. However, the polymers using catalyst containingligands rather than oxalate were less bright and more yellow. Therefore,the oxalate embodiment of the present invention is preferred over theligand containing embodiment of the invention.

[0093] In comparing examples 5, 15 to 18, although catalysts containingH, Li, Na, K, and Ca can polymerize BHET in a similar rate, Licontaining catalyst produced the least amount of acetaldehyde in theresulting polymer and are therefore preferred.

[0094] In comparing examples G, 19 and 20, the germanium catalyst can beenhanced by potassium oxalate.

We claim:
 1. A catalyst combination comprising a titanyl oxalate of theformula X_(m)TiO(C₂O₄)₂(H₂O)_(n), where each X is independently selectedfrom the group consisting of: H, Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba,and ammonium m=1 or 2 and a catalyst enhancer comprising oxalic orcarboxylic acid containing 1 to 26 carbon atoms or their correspondingLi, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba or ammonium salt.
 2. An enhancedcatalyst comprising a titanium compound of the formula X_(m)TiY_(o) X isselected from the group consisting of: H, Li, Na, K, Rb, Cs, Be, Mg, Ca,Sr, Ba and ammonium, m=1 or 2, Y is a ligand of the formulaC_(a)H_(b)O_(c), a=0 to 30, b=0 to 60, and c=1 to 10; o=2, 3, 4, and acatalyst enhancer of an oxalic acid or its corresponding Li, Na, K, Rb,Cs, Be, Mg, Ca, Sr, Ba or ammonium salt.
 3. The catalyst of claim 1further comprising an additional catalyst enhancer of a compoundcontaining antimony or germanium.
 4. The catalyst of claim 2 furthercomprising an additional catalyst enhancer of a compound containingantimony or germanium
 5. An enhanced catalyst combination comprising anantimony containing catalyst and a catalyst enhancer of oxalic acid orits corresponding Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba or ammoniumsalt.
 6. An enhanced catalyst combination comprising a germaniumcontaining catalyst and a catalyst enhancer of oxalic acid or itscorresponding Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, B a or ammonium salt.7. The catalyst combination of any of claims 1 through 4 wherein theconcentration of titanium is from 0.1 to 100 ppm.
 8. The combination ofclaim 1 wherein the catalyst enhancer is selected from the groupconsisting of lithium titanyl oxalate, potassium titanyl oxalate andammonium titanyl oxalate.
 9. The combination of claim 2 wherein thecatalyst enhancer is selected from the group consisting of lithiumoxalate, Li₂C₂O₄, sodium oxalate, Na₂C₂O₄, potassium oxalate, K₂C₂O₄,rubidium oxalate, Rb₂C₂O₄, and cesium oxalate, Cs₂C₂O₄.
 10. Thecombination of claim 1 wherein the titanyl oxalate is selected from thegroup consisting of metallic titanyl oxalates of the formulaM₂TiO(C₂O₄)₂(H₂O)_(n) wherein each M is independently selected frompotassium, lithium, sodium, cesium and a nonmetallic cation such asammonium.
 11. The combination of claim 1 wherein the catalyst enhanceris lithium oxalate and the titanyl oxalate is lithium titanyl oxalate.12. The combination of claim 5 wherein the antimony containing catalystis selected from the group consisting of antimony triacetate,Sb(CH₃COO)₃, antimony trisglycoxide Sb₂(OCH₂CH₂O)₃, antimony oxide(Sb₂O₃).
 13. The combination of claim 1, wherein the catalyst enhanceroxalate comprises from 0.1 part to 80 parts by weight of the combinationbased upon the weight of titanium.
 14. The combination of claim 2,wherein the catalyst enhancer comprises from 0.1 part to 80 parts byweight of the combination based upon the weight of titanium.
 15. Thecombination of claim 5, wherein the catalyst enhancer comprises from 0.1part to 80 parts by weight of the combination based upon the weight ofantimony.
 16. The combination of claim 6, wherein the catalyst enhancercomprises from 0.1 part to 80 parts by weight of the combination basedupon the weight of germanium.
 17. The combination of claim 3, whereinthe enhancer comprises from 0.1 part to 80 parts by weight of thecomposition.
 18. The combination of claim 4, wherein the enhancercomprises from 0.1 part to 80 parts by weight of the composition.
 19. Animproved process of producing a polyester by the catalyzedpolycondensation of polyester forming reactants in the presence of apolycondensation catalyst, wherein the improvement comprises utilizingas the catalyst the combination of claim
 1. 20. An improved process ofproducing a polyester by the catalyzed polycondensation of polyesterforming reactants in the presence of a polycondensation catalyst,wherein the improvement comprises utilizing as the catalyst thecombination of claim
 2. 21. An improved process of producing a polyesterby the catalyzed polycondensation of polyester forming reactants in thepresence of a polycondensation catalyst, wherein the improvementcomprises utilizing as the catalyst the combination of claim
 5. 22. Animproved process of producing a polyester by the catalyzedpolycondensation of polyester forming reactants in the presence of apolycondensation catalyst, wherein the improvement comprises utilizingas the catalyst the combination of claim
 6. 23. An improved process ofproducing a polyester by the catalyzed polycondensation of polyesterforming reactants in the presence of a polycondensation catalyst,wherein the improvement comprises utilizing as the catalyst thecombination of claim
 7. 24. An improved process of producing a polyesterby the catalyzed polycondensation of polyester forming reactants in thepresence of a polycondensation catalyst, wherein the improvementcomprises utilizing as the catalyst the combination of claim
 9. 25. Animproved polyester containing the combination of claim
 1. 26. Theimproved polyester of claim 24 wherein the catalyst combinationcomprises from 0.1 part to 80 parts per million of the polyester. 27.The improved polyester produced by the process of claim
 19. 28. Animproved polyester containing the composition of claim
 2. 29. Theimproved polyester of claim 24 wherein the polyester is polyethyleneterephthalate.
 30. The combination of claim 1 dissolved in a solvent 31.The combination of claim 30 wherein the solvent is ethylene glycol.